Tone reception for carrier telegraphy



R. B. SHANCK TONE RECEPTION FOR CARRIR TELEGRAPHY Filed July 9. 1928 Oct. 28, 1930.

Patented Oct. 28, 1930 UNITED STATES PATENT *oFFic-E,

ROY is.` sHANOK, or FLUsHINa,l New YORK, AssreNoR To AMERICAN TRLEPHONRAND I i TELEGRAPH- COMPANY, A OORPORATIONOF Naw YORK f,

'i1-ONE REoRrrioN ROR CARRIER' TELEGRAPHY Appiiaan inea' muy a,

This invention relates tothe art of telegraph coinmunication'and discloses an improve method of reception applicable chiefly to carrier current telegraphy whereby the signals are read by means of a` tone instead of the usual sounder clicks. `This method of reception is similar to that einplo-yed in the majority of radio receiving stations.`

In carrier current telegraph systemseach subscribers telegraph station is in generalv connected to a local central Oiiice over a sub*- scribers loop. Two distant subscribers stations are connected together by means of-an interconnecting trunk vcircuit extending between 'the receptive central Ollices. A sender key located at each station controls a direct current signaling circuit operating Vover 'the subscribers loop and applies a source of alt-ernating current potential 4to rthe toll circuit in accordance with the operation of the sender key; At the distant central oilice the received Y alternating current is rectified and caused to operate direct current signaling means at said Y central oliice which in turn operates theusual DIC. telegraph sounder mechanism at the distant subscribers station. A considerable amount of expensive equipment is thus re-fy quired at the receiving terminal of the toll cir-4 cuit to translate the alternating current pulses into Vclicks on the sounder. This equipment could be eliminated by'using theftone method of reception. f j With the to-ne method of reception theonly receiving apparatus required at the subscribvf r ers station would be an ordinariy telephone" receiver7 while at the centraloilice no trans" latingapparatus `would be required if tone transmitted from the sending station were in the audio frequency range. Even where this`` is not the case the D. C. receiving signal equipnient would be eliminated at the central ot-` ice, thecarrier currentpulses being merely demodulated to a suitable frequency for tone4 reception.` i

In addition to the economies in terminal apparatus, thetone method oli-reception Offers i The system would lend it itself readily to the connection of branch lines; without the necessity of repeaters VVhaving other advantages.

1928. sei-iai No. 291,251. f

movable parts. Furthermorethe supply of availableV operators should be greatly increasedinasinuch as there are now many professional and amateur radio operators who are skilled in tone reception but are unable to read sounder signals. The'number of persons learning sounder reception, it-might be added, is now almost negligible. i v

The system employing tone -reception'is best l the operation of relay 5 at oice C by opening V and closing the operating lcircuit thereof. The operation of rela-yl upon depression of keyQ transmits tone from source 7 to stations VA and B through winding 6 inductively coupled to the other twoI windings of transformer 4. Releaseof key 2 in turn releasing relay 5 opens the circuit containing tone source 7 and thus prevents the'further transmission of tone to 'stationsA and B. VThe purpose of transmit- 'f vting tone to station A to enable the operator there to monitor 'bymeans of' receiverl and thus jdetermiiie thelcorreetnessof the transmitted message.` The operatorat :stationv reads the-received signals by' listening with receiverQ. j i Y n y i r" theioperator atstation B desirestotransmit a 1iuessage,fhe` Operatesley in turn operating relaylOeto transmittone from source 21to Vstationsfl;y andV B through windiiig12 oftransformerxlf). Q Y i f A i' V Filtersl-and 1 8/ passthe frequencyfrom tone sources 7 and 21 and a narrow .band extending above and below this-frequency but Vsuppress .other frecpieneies and thus permit otherte'legraph channels tobe Operated over toll circuit llwithoutinterfering with signalst'ransinitted between stations A and B. ther channels Iiwired in va manner identical with that shown for stations A and B are connected to leads 11 and 14C respectively. Each channel thus connected operates on a difterent frequency from any other channel and is of course equipped with suitable filters to prevent interference from other channels.

Itis sometimes desirable that a station on a branch circuit be able to communicate with stations A and B. This is accomplished by connecting such a branch circuit at an intermediate point on the main circuit as indicated by leads 19. The branch station is of course equipped with the same type of iilter and other terminal equipment as is used for station A or B. A transformer is usually inserted in leads 19 in order to match up the impedance relations.

In F ig. 1 the circuit is arranged for halt-- duplex operation which means that only one message at a time can be transmitted between stations A and B. Fig. 2 also discloses a circuit arranged forhalf duplex operation, but one which utilizes a four wire circuit between central oiiices. In Fig. 2, key 2 controls the operation of relay 5. vWith the key depressed, source of tone 30 is applied to circuit 84 through resistance 31. This tone is transmitted to receiver 9 at station B. Simultaneously therewith tone from source 30 is also applied to winding 6 or' transformer 4 and is thus transmittedr toA receiver 1 at station A to enable the operator there to rea d the transmitted message. With key 2 released, the release of relay 5 connects a. short circuit across the input to circuit 34 and thus prevents the further transmission of tone to receiver 9. The release of key 2 also disconnects winding 6 from tone source 30. The operation of key 8 at station B causes tone from source 32 to be transmitted to station B over circuit 35 and to station A over loop 17.

Fig. 2 may be converted into a full duplex system by disconnecting windings 6 and 12 from tone sources 30 and 32, respectively. W ith this change accomplished, the operation of key 2 would transmit tone to receiver 9 only, and theoperation ofkey 8 would transmit tone to receiver 1 only. Thus, two messages could be simultaneously transmitted over the circuit between stations A and B without interference, one in each direction. The disadvantage or" this arrangement would lie in the fact that the operator transmitting a message could not hear his own signals.

This diiiiculty could be avoided by transforming the four wire circuit into tWo` separate one-way circuits. For example, if two circuits silnilar to Fig. 1 were connected between stations A and B, omitting from one such circuit key 8 and the tone equipment at office D, i. e., relay 10, winding 12 and tone 21, and omitting from the second circuit simi- 'i transmitting operator could hear the transmitted signals. These circuits, of course, would require only one-way repeaters in place of the two-way repeater 20, shown in F ig. 1. For the first of the above circuits, the repeater would transmit in the direction from station A to station B, and in the reverse direction for the second circuit. With the irst such circuit,for example, the operation of key 2 would transmit tone to the receivers at stations A and B associated with said first circuit, while with the second circuit the operation of key 8 would similarly transmit tone to the receivers atboth stations associated with the second circuit.

What is claimed is:

1. In a telegraphsystem, in combination, a telegraph circuit extending from a first point through intermediate central oilices to a second point, a telegraph sending key and a telephone receiver associated with said telegraph circuit at the first point, a telephone receiver associated with said telegraph circuit at the second point, and means at said central ofiices adjacent the first point for transmitting a tone to both said receivers in accordance with the operation of said telegraph key.

2. In a telegraph system, in combination, a telegraph4 circuit extending from a first point through intermediate central ofiices to a second point, a telegraph sending key and a telephone receiver associated with saidv telegraph circuit at each of said points, means at the central oiice adjacent the first point for transmitting a tone to the receiver at the second point in accordance with the operation of the telegraph key at the i'irst point, and means at the central oiiice adjacent the second point for similarly transmitting tone to the receiver at the first point in accordance with the operation of the telegraph key at the second point.Y

3. In a telegraph system, in combination, a telegraph circuit extending from a first point through intermediate central` oiiices to a second point, a telephone receiver and a telegraph sending key associated with the telegraph circuit at each said point, means at the central ofiice adjacent the first point for transmitting tone to the receiver at each poi nt in accordance with the operation of the telegraph key at the first point, and similar means at the central oi'iice adjacent the second point for transmitting tone to the receiver at each point in accordance with the operation or' the telegraph key at the second point.

1. The method of telegraph comnnmication which consists in transmitting from a sending station to a central ofiice paises of direct current to represent signals in accordance with a predetermined code, causin said current pulses to operate alternating current means at the central oflice to produce alternating'current pulses proportional in lei l. to saidv direct current pulses, and causi said alternating current pulses to ope 'ate 'i (if,

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acoustical means at the receiving station to produce tones proportional in length to said current pulses.

5. Th-e method of telegraph communication Which consists in transmitting 'from a sending station to a central olice pulses of direct current to represent signals in accordance With a predetermined code, causing said current pulses to operate alternating current means at the central oiiice to produce alternatn ing current pulses proportional in length to said direct current pulses, and causing said alternating current pulses to produce in telephone receivers at said sending Vstation and at a distant receiving station audible tones proportional in length to said transmittedl pulses. Y

6. In the art of telegraph communication, a telegraph circuit extending from a tirstte a second point, a telegraph sending key and l a telephone receiver associated With said circuit at each said point, means located at a third point remote from said other vpoints and under control of said key at the lirst point to transmit tone to the receivers at said first and second points in accordance with the operation of said key, and means located at a 'fourth point remote from said other points and under control ot said key at the second point to similarly transmit tone to the receivers at said iirst and second points in accordance With the operation of said key at said second point.l

7. In the art of telegraph communication, atelegraph circuit'extending from a iirst point to a second point, a telephone receiver and a telegraph sending key associated With said circuit at said first point, a telephone receiver associated with said circuit at said second point, and means located at a third point remote from said other points andr under control o't'said key at said irst point for transmitting a tone to both said receivers in accordance with the operation oi'l said key.

8. In the art of' telegraph communication, a telegraph circuit extending from a lirst pointto a second point, atelegraph sending key at said iirst point and a telephone receiver at the said second point associated With said circuit, and means located at a third point remote from said other points and under control of said key for transmitting a tone to said receiver in accordance with the operation of said key.

9. In the art of telegraph communicaticn,a telegraph trunk. circuit extending between tivo o'ices, loop circuits individual thereto at each otce and extending respectively each to Y a local telegraph subscrihers statiomf'a telegraph sending key and a telephone receiver associated With said loop at each said station, a source of :tone associated With the telegraph circuit at each oiiice. relavv means at each o'liice controlling the output of Vthe corresponding tone source, an Voperating circuit for each said relaymeans including the loop circuit terminatingat said oftice and the sending key associated with said loop, and means to transmit tone ironia given said source to the receivers at `lcoth stations, in accordance With the operation of said sending` key controlling said tone source. i

l0. In the art of telegraph communication, Va telegraph trunk circuit extending between tvvo oices, a loop circuit connected thereto at eacli office: and extending each to a local suhscriherstelegiaph station, a telegraph se"iid-Y ing key and a telephone receiver associated" with the loop at one station, a telephoneie, ceiver associated with the loopat the second statioii,aisource ot'tone'as'sociated with the telegraphcircuit at the 'office adjacent the jlirst station, relay means atsaid oilice controlling the output of said source, an operat- .Y

ing circuit for said relay means including Vthe loop circuitterminating at said oliic'e and i said sending Vloop connected thereto, fand means to transmit said tone tohoth receivers in accordance with the operation of said key.

1l. In the art` of telegraph communica?A tiona telegraph trunk circuit extending hetWe'en two offices, loop circuits individual thereto at each office extending each to a local subscribers telegraph station individual to said loop,.a telephone receiver and a v telegraph sending key ,associatedfwith said loop at each station,a source ottone at each oliice associated Withthe telegraph circuit, relay means at eachothce controlling said- Vtone source,.an operating circuit for each said relay meansiin'cluding thenloop circuit terminating at'the corresponding oiice and the sending key connected to said loop,and means to transmit tone from the ,source at eitheroticeto they receiver` atV the stationadjacent thel distant oiice in accordance with tion, and means located at a point yremote Y froinsaid stations and controlled by the ,a .telegraph circuitextending from a first toVv iii,-

sending `key at `any saidlirst station for transmitting toneVV`V to allsaid receivers-'in accordance with the operation of said fsend- `13. In a telegraph system, incomhination,

ya .telegraph circuit extending Vfrom alrstv to a secondA station, a `branch A telegraph icir'- cuit connectingfvvith said first circuit and extending Vtoma ,third station, a telegraph sending key and a telephone receiver` asso- Y cia-ted WithV said circuitat 'each saidstation,` and means locatedata point remote from said stations `and controlled from the sending key at any said station for transmitting tone to all said receivers in accordance with the operation of said sending key.

14. In a telegraph system, in combination, a telegraph circuit extending from a first point through intermediate central ofiices to a second point, a receiver associated with said telegraph circuit at the second point, a receiver and an induction coil associated with said telegraph circuit at the irst point, a telegraph sending key connected from the midpoint of one of the windings of said induction coil to ground, a second induction coil associated with said telegraph circuit at the central oiiice adjacent the first point, relay means and a source of current connected from the midpoint of one of the windings of said second induction coil to ground, a tone source controlled by said relay means in accordance with the operation of said sending key, and means con necting said tone source to said telegraph circuit.

15. In a telegraph system including a sending station, `a central station and a single loop circuit interconnecting said stations, in combination, a sending key at said sending station, a tone source at saidv central station, and means controlled by said sending key for causing said tonesource to transmit tones over said loop circuit in accordance with the operation of said sending key.

16. In a telegraph system including a sending station, a receiving station, a central station and a single loop circuit connected between said central station and said sending and receiving stations, respectively, in combination, a sending key at said sending station, a tone source at said central station, and means controlled by said sending key -for causing said tone source to transmit tones over said loop circuits to said sending and receiving stations in accordance with the operation of said sending key.4

17. In a telegraph system, in combination, a telegraph circuit extending from a iirst 'point through intermediate central ofices to a second point and having a single loop circuit extending from each said point to the central oiiice adjacent said point, a telephone receiver and a telegraph sending key associated with the telegraph circuit at each said point, means at theA central office adjacent the iirst point for transmitting toneA to the receiver at each point in accordance with the operation of the telegraph key at the first point, and similar means at the cen tral station adjacent the second pointV for transmitting tone to the receiver at each point in accordance with the operation of the telegraph key at the second point.

In testimony whereof, I have signed my name to this 'specification this Gthfday of July, 1928. Y

ROY B. SHANCIAI. 

